Chlorofluorocarbon (CFC) based chemicals have been widely use in industry in a variety of different applications including as refrigerants, aerosol propellants, blowing agents and solvents, among others. However, certain CFCs are suspected of depleting the Earth's ozone layer. Accordingly, more environmentally friendly substitutes have been introduced as replacements for CFCs. For example, 1,1,1,3,3-pentafluoropropane (HFC-245fa) is recognized as having favorable physical properties for certain industrial applications, such as foam blowing agents and solvents, and therefore is consider to be a good substitute for the CFCs previously used for these applications. Unfortunately, the use of certain hydrofluorocarbons, including HFC-245fa, in industrial applications is now believed to contribute to the global warming. Accordingly, more environmentally friendly substitutes for hydrofluorocarbons are now being sought.
The compound 1-chloro-3,3,3-trifluoropropene, also known as HCFO-1233zd or simply 1233zd, is a candidate for replacing HFC-245fa in some applications, including uses as blowing agents and solvents. 1233zd has a Z-isomer and an E-isomer. Due to differences in the physical properties between these two isomers, pure 1233zd(E), pure 1233zd(Z), or certain mixtures of the two isomers may be suitable for particular applications as refrigerants, propellants, blowing agents, solvents, or for other uses.
1,3,3-Trichloro-1,1-difluoropropane (HCFC-242fa or simply, 242fa) can be either a starting material or an intermediate (if starting with a less fluorinated chlorocarbon, e.g., HCC-240fa, 1,1,3,3-tetrachloropropene, 1,3,3,3-tetrachloropropene, and/or 1,1,3,3-tetra-chloro-1-fluoropropane) in the production of both 245fa and 1233zd which are well known in the art as described in U.S. Pat. Nos. 5,763,706 and 6,844,475, respectively. In the case of 1233zd, see U.S. Patent Pub. No. 2011-0201853. These documents are hereby incorporated herein by reference.
It has now been found that an important feed stock or intermediate in the production of both 245fa and 1233zd, is an azeotrope or azeotrope-like mixture of 1,3,3-trichloro-1,1-difluoropropane (HCFC-242fa) and hydrogen fluoride (HF). This intermediate, once formed, may thereafter be separated into its component parts by extraction or distillation techniques. HCFC-242fa has a boiling point of about 109° C. and HF has a boiling point of about 20° C., at standard atmospheric pressure. The azeotropic or azeotrope-like compositions find use not only as reactor feeds in the production of 245fa and 1233zd, but they are additionally useful as solvent compositions for removing surface oxidation from metals.